Nitrones oxaziridine ring

The nitrone-oxaziridine ring-chain isomerization has attracted theoretical attention.The quantum yield for the reaction has been measured and the reaction has been examined in a rigid polymer matrix. ... 

Without additional reagents Cyclic nitrones from oxaziridine ring and reverse isomerization... 

Simple oxaziridines and diaziridines do not absorb in the near UV. Lack of absorption was one argument to distinguish between true three-membered ring structures and unsaturated open chain isomers like nitrones or hydrazones. 

Diarylnitrone (31) formation from N-substituted, diaromatic imines has been recognized to require the presence of NADPH/O2, and has been proposed to proceed via the intermediacy of an oxaziridine3 possibly arising from reaction of the parent imines with the putative P-450 [FeO]3+ species in analogy to the oxidation of olefins118. Ring cleavage of the oxaziridine then yields nitrone or amide (equation 10). 

The third chapter on Oxaziridines is an expose of this labile ring system containing both an oxygen and a nitrogen heteroatom and its equilibration with the isomeric nitrone system. 

Treatment of C-aryl oxaziridines (e.g., 109) with dilute acid causes C—O bond fission to the corresponding nitrone 108. However, similar treatment of C-alkyl oxaziridines (e.g., 112) leads to the 1,4-dicarbonyl compound (e.g., 113) by N—O bond fission.The mode of ring opening is influenced by the stabilization of the positive charge resulting from initial protonation on oxygen. 

Similarly, oxidation of 171 gives the dioxazabicyclohexane 172 which was only stable below — 20°C. Exposure of the compound to silica gel resulted in ring opening of the oxaziridine, to give the nitrone 173. ... 

Acid-catalyzed hydrolysis of A-aryloxaziridines may proceed via cleavage of either the C—O or N—O bonds, depending upon the ring substitution pattern. These reactions are usually discussed in terms of initial protonation at the oxaziridine oxygen atom <77JHC1393>. Acid-catalyzed isomerization to nitrones has also been reported <64HC(19)624>. 

During the last 10 years many additional oxaziridines have been isolated after photolysis of nonaromatic nitrones. The three-membered ring isomers of heteroaromatic A-oxides proved to be too reactive for direct detection but... 

The steric course of oxaziridine formation was investigated by Splitter et al. Only one out of two feasible disrotatory processes of nitrone 71 is observed, bringing the outer substituents R and R" on the same side of the ring. An observed unspecificity of ring closure products may be accounted for by prior E-Z isomerization of the nitrone. 

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